Electrodialysis apparatus with reversal of polarity



y 1 1962 J. R. OLlE ETAL 3,04

ELECTRODIALYSIS APPARATUS WITH REVERSAL 0F POLARITY Filed April 5, 1960 2 Sheets-Sheet 1 INVENTORS' JACOB RUURD OLIE PETER JOHAN VAN WINSEN ATTORNEYS July 10, 1962 J. R. our: ETAL. 3,043,768

ELECTRODIALYSIS APPARATUS WITH REVERSAL OF POLARITY Filed April 5, 1960 2 Sheets-Sheet 2 FIG.2

l ii 41 FIG.3

INVENTORS JACOB RUURD OLIE PETER JOHAN VAN WINSEN A T TOR NEYS United States Patent 3,043,768 ELECTRODIALYSIS APPARATUS WITH REVERSAL 0F POLARITY Jacob Ruurd Olie, Santpoort, and Peter Johan van Winsen, Haarlem, Netherlands, assignors to N.V.

Bronswerk, Amersfoort, Netherlands Filed Apr. 5, 1960, Ser. No. 20,118 Claims priority, application Netherlands Apr. 8, 1959 2 Claims. (Cl. 204-301) The invention relates to a multicompartment electrodialysis apparatus, Such an apparatus comprises alternating desalting compartments (which may also be called diluting compartments) and concentrating compartments, bounded by alternately positioned positive and negative ion-permeable membranes, which are spaced apart, at their peripheries, by supple cell packings or cell-frames and by membrane supports or spacers within each cell to form a membrane stack, which is flanked on either side by an electrode chamber containing an electrode. Frequently, each of said electrode chambers is rinsed by a separate liquid.

This cell-unit is clamped between two endplates, for example by means of drawbars mounted between said endplates.

The membrane stack may sometimes be interrupted by rigid frames positioned at intervals in the membrane stack, which rigid frames may be provided with separate inlet and outlet liquid connection pipes for the liquids.

It is known, that in such a stack of membranes in the course of time deposits may be formed on or in the membranes, which cause the electric resistance to rise too high, in particular, when calcium-containing liquids are treated. It is known that said phenomena may be cured by now and then reversing the polarity of both electrodes and simultaneously exchanging the supply as well as the discharge of the concentrating and the diluting chambers and if necessary those of the electrode rinsing liquids. To this end not only the current connections must be exchanged but also a large number of taps must be closed and others must be opened.

The object of the invention is to provide an improved apparatus, in which the operation of reversal of polarity is reduced to a simple action.

Another object of the invention is to provide a simple unit which can be operated by hand by unskilled persons.

Further objects of the invention will appear from the following description.

The present invention mainly consists in that all of the liquid connections and both the electric connections are fed via one of the two endplates and via a connection plate which is fastened to said endplate so as to be detachable by a simple action and that in such a manner that, when the connection plate is rotated over a certain angle with respect to the adjoining endplate the connections for the electric current as well as the liquid connections for the desalting and concentrating compartments and those for the electrode chambers have all been interchanged.

Obviously, during the rotation of the connection plate the various pumps in the liquid pipes should be stopped.

Although the present invention may be employed in apparatus of high capacity, it is particularly important for small, easily manageable units.

The invention is elucidated with the aid of a drawing, representing a simple embodiment of the invention, in which:

:FIG. 1 is a longitudinal cross-section of the apparatus on the line I-I in FIG. 2;

FIG. la is a detail of the current path;

FIG. 2 is a front view of the end plate provided with the passage-ways for all the liquids and for the electric current; and

FIG. 3 is a rear view of'the connection plate; FIG- URES 2 and 3 being drawn on a smaller scale than FIG- URE 1.

In FIG. 1 the two end plates are indicated by reference numerals 1 and 2. Said end plates are, as is usual, made of a hard, electrically non-conductive material such as polyethylene, polyvinyl chloride or polyester. The membrane stack is positioned against these two plates, said membrane stack comprising alternately disposed positive and negative selective membranes 3 and 4, spaced apart by supple cell frames 5 and separators 6. Out of the four manifold channels for the supply and discharge of concentrate and dialysate which run through the membrane stack only channel 8 is visible in FIG. 1. This channel is in a known way in open liquid connection with the series of alternating compartments 14 and, by means of packing rings 9, it is blocked from liquid connection with the other series of compartments 15. The electrode 10 is placed in the electrode chamber 11 and the electrode 12 in electrode chamber 13. Now if the electrode 10 in the left part of FIG. 1 is positive with respect to the electrode 12, and the membranes 3 show a positive selectivity and the membranes 4 a negative selectivity then the compartments 14 are concentrating compartments and the compartments 15 are desalting compartments. The anions go to the left and are let through by the positive membranes 3, but not by the negative membranes 4; the cations go to the right and are let through by the negative membranes 4, but not by the positive membranes 3, so the compartments 15 having a positive membrane to. the left and a negative membrane to the right are desalting or diluting compartments and the compartments 14 having a negative membrane to the left and a positive membrane to the right are concentrating compartments. When the polarity of the electrodes is reversed, then a compartment 14, having a positive membrane to the right and a negative membrane to the left is changed into a desalting compartment.

The electrode 10 is provided with a current supply pin leading through plate 1. Electrode 12 has a cur-rent supply pin 17, which is led through plate 2 and which is connected with a pin 18 mounted on the plate 1, via bores 19 in plate 2 and bores 20 in plate 1 and via a liquid-tight connection 21-22 (see also FIGpla) which is situated outside of the membrane stack.

As is shown in FiGURES 2 and 3, plate 1 contains the apertures indicated by the numerals 23 to 30, inclusive, which in the position of the apparatus as shown in the drawings correspond with the apertures 31 to 38, respectively, in the connection plate 39.

The electrode chamber 13 in plate 2 is in liquid connection with aperture 24, via an opening in electrode 12, and via bores 40 in plate 2, connection piece 42, pipe 43, connection piece 44 and bores 45 in plate 1. At the opposite side of the plate 2 the electrode chamber 13 is in liquid connection with the aperture 28 in plate 1 in an analogous way. The apertures 26 and 30 give on to the electrode chamber 11 (to which end the electrode 10 is provided with openings in the same way as the electrode 12).

In the position represented in the drawing, the various apertures or" plate 39 are, for example, connected in the following manner (whereby the apertures in plate 1 which correspond therewith are added between brackets): 31(23) dialysate efiluent, 33(25) concentrate eflluent, 35(27) dialysate influent, 37 (29) concentrate infiuent; 32 and 34 electrode rinsing liquid eflluent (24 from plate 2, 26of plate 1, respectively), 36 and 38 electrode rinsing liquid influent (28 of plate 2, 30 of plate 1). In smaller installations the apertures 32, 33 and 34 can be connected to a common discharge pipe, and in the same way the apertures 36, 37 and 38 can be connected to a common supply pipe.

After the pumps present inthe liquid pipes have been stopped, two turn-buckles (which are not shown in the figure-but which are disposed on protrusions 62 of an exterior frame which further comprises the members 63 and 64 of angle iron, which bitch on to for instance two of the four extensions 46 of an angle steel frame 41, which is fastened on to the plate 1, and which turn-buckles keep the plates 1 and 39 clamped together, are now released by a simple action. After this, the membrane stack with its ends plates 1 and 2, which stack is joined to form a unit by a number of drawbars 65 co-operating with nuts 66, is taken apart, is rotated over 90 about an axis perpendicular to the end plates and, in the new position remounted onto the connection plate 39 by means of the said turn-buckles. In general it is not to be regarded as a drawback that by this action some loss of liquid is likely to occur. After the pumps and the current supply have been put into operation again electrodialysis is continued.

The connection plate 39 comprises four terminals 47 to 50, inclusive, for the supply of current, each of which is at its back side provided with a contact organ 61. When the plates land 39 are clamped together in any of the four possible relative positions, two adjoining contact organs are connected to the contact pins 16 and 18 of the end plate 1. The terminals 47 and 49 are for example connected to thepositive pole of the current source and the terminals 48 and 50 to the negative pole, so that in the position as drawn in the FIGURE 1, the electrode is negative and the electrode 12 is positive. When the two plates are rotated relative to each other over 90, the polarity of the electrodes is reversed.

As regards the liquid connections, the following open-' ings now correspond to and co-operate with one another: 23-33, 2434, 35, 2636, 27-37, 28-38, 29- 31-and -32.

The connections in plate 1 now are 23; concentrate efiluent, 25; dialysate influent, 27; concentrate influent, 29; dialysate eflluent, 24; rinsing plate 2 effluent, 26; rinsing plate 1 influent, 28; rinsing plate 2 influent and 30; rinsing plate 1 effluent. The connection 36 was previously connected With plate 2, electrode space 13 and is now connected with plate 1, electrode space 11 etc. After a subsequent dialysis period the membrane stack can be again rotated over 90", preferably always turning in the same direction, so that all the manifold channels passing through the membnanes alternately serve as supply channels and as discharge channels, and so that it becomes possible for any solid impurities proceding from the waste water which may be carried along in the channels to be rinsed farther outward. The pollution of the dialysate which may hereby be caused generally is so slight percentually that the result of this process is a good usable drinking water, particularly when a bufifcr supply is used, which when employed in a lifeboat may advantageously contain for instance 80 litres.

In the embodiment shown in the drawing, short tube pieces 51 and 52, are provided on plate 1, and are arranged in the said apertures which tube pieces fit against packing rings 53 and 54 made of a resilient material such as soft rubber. A good leak-proof and water-tight fitting together of the plates 1 and 39 when they are clamped on to each other can, however, be carried out in various ways. For the sake of getting a good centrage of the two plates 21- ring 55 having earns 56 is mounted on the of 15 x 15 cm., a capacity of l. of drinking water in 8 hours, starting from sea water, was obtained. Hereby the average current intensity was 2.75 A. to 40 volt. The unit has been developed more particularly for use in a lifeboat. The capacity is amply suflicient for a longboat for 60 persons (the minimum requirement for drinking water being /2 .l. per head per day).

As such a unit will be provided with one single sieve for the sea water only, the interior will, after some time, be contaminated by organic material, and also the wellknown deposits on the membranes will gradually develop. If now by a simple action the entire apparatus is reversed, for example every 2 or 3 hours, any contaminations which may have entered will be rinsed out and any deposits formed will be dissolved again. Moreover, the apparatus will always be ready for immediate use and in addition to this, it can serve for a period of several days orif necessaryweeks. It is possible to provide the liquid supply pipes with hand pumps (for instance the well known wing pumps) and to generate the direct current for the apparatus with the aid of a hand-driven dynamo.

If operation is effected with two separate electrode liquids, a concentrating liquid and a desalting liquid (dialysate), the connection plate and the adjoining end plate are each provided with eight liquid connection pipes as described above, in such a way, that at a rotation of said plates relative to one another over an angle of the reversal .of polarity has been effected. In larger plants, which for example have additional and separate supply and discharge connections for liquids halfway the membrane stack or otherwise, the number of liquid connections of the connection plate may be proportionally larger.

We claim:

1. An improved electrodialytic multi-compartment apparatus comprising a plurality of ion-permeable membranes alternating with flexible frames to form a membrane stack comprising a plurality of narrow compartments bounded on their opposite major faces by said membranes and around their peripheries by said flexible frames; manifold channels leading through series of registering holes in the membranes to constitute continuous passages for the supply and discharge of liquids to the compartments; electrodes for the passage of current through the membrane stack; end plates at both ends of the stack having electrodes; means clamping the unit together in a liquid-tight manner, the improvements consisting in that all the liquid connection pipes for efiluent and influent liquids as well as the electric connection leads to the electrodes are mounted so as to lead through one of the two end plates and through a connection plate adjoining the said one end plate, means for detachably clamping said connection plate onto the said ad joining end plate in a liquid-tight manner, said pipes being situated in the said adjoining plates in such a way that after releasing the connection plate from the adjoining end plate and rotating said adjoining plates with respect to each other over a certain angle and clamping said adjoining plates'to each other in the said new position the connections for the electric current as well as the liquid connections for the various liquids are interchanged in a predetermined way.

2. An electrodialytic multi-compartment apparatus as claimed in claim 1, in which the connection plate as well as the adjoining end plate are provided with two alternating setsof four apertures being positioned at distances from the centre of the said plates, said distances being of each pair of corresponding apertures when the said 5 adjoining plates are clamped together.

References Cited in the file of this patent UNITED STATES PATENTS 2,059,283 Saar Nov. 3, 1936 2,792,559 'Maberry May 14, 1957 2,863,813 Juda Dec. 9, 1958 

1. AN IMPROVED ELECTRODIALYTIC MULTI-COMPARTMENT APPARATUS COMPRISING A PLURALITY OF ION-PERMEABLE MEMBRANES ALTERNATING WITH FLEXIBLE FRAMES TO FORM A MEMBRANE STACK COMPRISING A PLURALITY OF NARROW COMPARTMENTS BOUNDED ON THEIR OPPOSITE MAJOR FACES BY SAID MEMBRANES AND AROUND THEIR PERIPHERIES BY SAID FLEXIBLE FRAMES; MANIFOLD CHANNELS LEADING THROUGH SERIES OF REGISTERING HOLES IN THE MEMBRANES TO CONSTITUTE CONTINUOUS PASSAGES FOR THE SUPPLY AND DISCHARGE OF LIQUIDS TO THE COMPARTMENTS; ELELCTRODES FOR THE PASSAGE OF CURRENT THROUGH THE MEMBRANE STACK; END PLATES AT BOTH ENDS OF THE STACK HAVING ELECTRODES; MEANS CLAMPING THE UNIT TOGETHER IN A LIQUID-TIGHT MANNER, THE IMPROVEMENTS CONSISTING IN THAT ALL THE LIQUID CONNECTION PIPES FOR EFFLUENT AND INFLUENT LIQUIDS AS WELL AS THE ELECTRIC CONNECTION LEADS TO THE ELECTRODES ARE MOUNTED SO AS TO LEAD THROUGH ONE OF THE TWO END PLATES AND THROUGH A CONNECTION PLATE ADJOINING THE SAID ONE END PLATE, MEANS FOR DE- 